In many spray applications, such as humidification or evaporative cooling, it is desirable to generate relatively fine spray particles so as to maximize surface area for distribution in the atmosphere. For this purpose, it is known to use air assisted spray nozzle assemblies in which a pressurized gas such as air is used to break down or atomize a liquid flow stream into very fine liquid particles. For example, in some air assisted nozzle assemblies the liquid is mechanically broken down primarily in an atomizing chamber located in the nozzle assembly upstream from a spray tip or air cap which serves to form the discharging spray pattern. Alternatively, the liquid particle break down can occur in the air cap itself.
From an efficiency and economic operating standpoint it is also desirable that such particle breakdown be effected using relatively low air flow rates and pressures. Heretofore this has created problems. In particular, spray tips or air caps which provide efficient and economic operation are generally relatively complex in design, and hence relatively expensive to produce.
Additionally, these air caps are also very limited in terms of flexibility of use. For example, such air caps are typically designed so that they can only be used with a specific air assisted nozzle body configuration. Accordingly, differently configured air caps must be provided for each type of nozzle. Moreover, such air caps cannot be easily customized to discharge the liquid in different spray patterns.
Another problem with existing air assisted spray nozzles, and in particular nozzles used for spraying a coating or paint onto a surface, is that the high air pressure necessary to breakdown the fluid particles results in a high nozzle discharge pressure. This high discharge pressure often causes the particles to bounce back from the surfaces upon which they are applied. This not only can adversely affect the applied coating and create waste in material, but also can create an environmental hazard by virtue of the spray particles which are discharged into the surrounding ambient air.
Still a further problem with existing air assisted spray nozzles is that to achieve necessary atomization it often is necessary that pressurized air streams be directed against the liquid stream in a manner that produces a flat spray pattern. On the other hand, it often is desirable that the spray have an outwardly opening conical spray pattern, with finely atomized particles distributed throughout a full cone. Heretofore it has not been possible to achieve such full cone spray patterns at low air pressures, such as 10 psi.